Controlling the dopant incorporation in a-axis oriented Co doped YBCO thin films

We studied the effects of Co doping (x = 0.22) on the intrinsic anisotropic properties of in-plane aligned a-axis YBa2Cu3-xCoxO7-delta films pulsed laser deposited on (100) LaSrGaO4 substrates. We used x-ray-absorption fine structure analysis and resistivity data to determine the quality of Co incorporation. Higher deposition pressures provided films with better Co dopant incorporation but smaller grain size. However at lower pressures proper Co incorporation can still be achieved by slowing down the cooling process. For transport along the c- direction, Co dopant causes reduction in interlayer coupling as evidenced by an increase in interlayer coupling as evidenced by an increase in resistive anisotropy (rho(c)/rho(b)) with increasing level of Co incorporation. Co doping level of x = 0.22 effectively doubles the resistive anisotropy of YBa2Cu3O7-delta films (from similar to 18 to similar to 40 at 100 K).